I have a bit of a different theory: I think we'll get more than just Senna's Lotus 98T. I'll elaborate.
Goodwood Festival has a statue in real-life, and it contains some models Lotus has used in F-1. From a classic Jim Clark car to a modern-era post-Genii Capital Lotus Renault. See pic below:
You can also see a Lotus from around the same era as the 98T, as well as Senna's 1987 yellow Lotus.
Now, if you go to the Goodwood Festival of Speed in-game, and go to Photo Mode on the track, you can find spots where you can clearly point your camera to the statue and check it with great detail, and one thing bothers me. The car models on the statue are very, VERY detailed, especially considering the objects around the statue. Too detailed for something you can barely see. Even the light reflections work almost the same way as it does on a playable car. It's almost as if they just shrunk models of the cars yet to be in-game, but have completed them already. And you can read some of the drivers' names too (I remember reading Jim Clark's). Also, guess which car was omitted from the statue in-game? The modern car, the one PD was less likely to have licensed. See in-game pics below:
Who used #12 Lotus 99T (the yellow one)? Senna.
I might be wild guessing here, but I think I'm on to something.